S1000D has a new and improved applicability mechanism based on the concepts of Applicability Cross Reference Table (ACT), Condition Cross Reference Table (CCT), and Product Cross Reference Table (PCT).
The ACT data module declares attributes of the product that are not likely to change during its life cycle such as model, series, and serial number. Examples of product attributes for a commercial aircraft include the manufacturer serial number and aircraft registration number.
The CCT data module declares technical, operational, and environmental conditions that can affect the applicability of technical content. Examples of these conditions are: service bulletin incorporation, location of maintenance, aviation regulations, temperature, wind speed, and sandy conditions.
The PCT data module lists actual physical product instances. For each product instance, the PCT specifies the values of product attributes and conditions pertaining to the product instance.
Applicability can be specified at the data module level inside the IDSTATUS or within the content of the data module at a more granular level such as a <step1> element. The ACT and the CCT are used as look up tables to lookup the relevant product attribute or condition as well as their allowed possible values. The applicability element then specifies the correct product attribute or condition identifier from the ACT or CCT and the values to test against.
The applicability information itself can be captured in human readable format for simple cases. For more complex cases, one or more assertions are used to specify the product attribute or condition to test and the values to test against. These values can be constrained with a pattern based on regular expressions as defined by the XML Schema specification.
The new S1000D applicability mechanism supports the "effectivity" requirements of civil aviation and provides capabilities that are beyond the ATA 2200 effectivity mechanism. It also facilitates the development of applicability filtering functionalties in Interactive Electronic Publications (IETPs). However, building an authoring front end that hides its complexity (regular expressions and logical operations) to the technical authors creating the content will be the key. This is also an area where well-defined business rules should be specified and enforced using a tool such as ISO Schematron.